The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft engine, which is generally of the turbojet engine type, is placed inside a nacelle which, among other functions:                provides the aerodynamic fairing of the engine,        allows channeling the external air toward the engine,        allows connecting the engine to the aircraft.        
Indeed, the nacelle generally exhibits a tubular structure comprising an air inlet upstream of the turbojet engine, a mid-section intended to surround a fan of the turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and accommodating, if appropriate, thrust reversal means.
Modern nacelles are intended to accommodate a bypass turbojet engine capable of generating via the blades of the rotating fan a hot air flow (also called primary flow) coming from the combustion chamber of the turbojet engine, and a cold air flow (secondary flow) which circulates outside the turbojet engine through an annular passage, also called flow path, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine from the rear of the nacelle.
The downstream section of a nacelle for such a turbojet engine generally exhibits a fixed outer structure, called Outer Fixed Structure (OFS) and a concentric fixed inner structure, called Inner Fixed Structure (IFS), surrounding a downstream section of the turbojet engine accommodating the gas generator of the turbojet engine.
The fixed inner and outer structures define the flow path intended to channel the cold air flow which circulates outside the turbojet engine.
In a particular case of a cascade-type thrust reverser device, the means implemented to perform redirection of the cold air flow comprise cascade vanes of the cold air flow and a cowl.
This movable cowl is displaceable between, on the one hand, a deployed position in which it opens a passage within the nacelle intended for the diverted cold air flow, and on the other hand, a retracted position in which it closes this passage, the cowl having only a simple sliding function aiming to uncover or cover these cascades.
More precisely, the thrust reverser device comprises two semi cylindrical half-cowls, mounted so as to be able, in particular during maintenance operations, to be open «like a butterfly» by pivoting around a longitudinal hinge line, in the vicinity of a nacelle suspension pylon by which the nacelle is connected to the wing or to the fuselage of the aircraft.
Such a structure is called C-duct.
Each one of the two half-cowls is slidably mounted on a half-beam pivotally mounted on the pylon, the rotational movement of each half-beam on the pylon providing pivoting of each half-cowl relative to this pylon for the maintenance operations.
The sliding movement of each half-cowl on its associated half-beam allows making the thrust reverser pass from the direct jet configuration to the reverse jet configuration, and vice versa.
Each half-beam comprises, typically, on its outer face, primary and secondary rails capable of allowing movement of the associated half-cowl, and a plurality of hinge clevisses capable of allowing articulation of the half-beam 1 on the associated pylon.
The assembly formed by the half-beam, its rails and its hinge clevisses, is often referred to as 12 o'clock structure, given its position at the top of the circle defined by a nacelle section, and by analogy with the dial of a clock.
Moreover, in order to provide the aerodynamic continuity of the lines of the nacelle and because of an interference with the wing of the aircraft during the reverse jet phases, an aerodynamic fairing panel can be mounted on either side of the suspension pylon, by surmounting, at the upper portion, the half-cowls.
Each one of these panels is connected to the beam at the side of the interference with the wing, or connected to the cowl at the side opposite to the interference.
Due to the presence of the removable aerodynamic fairing panel between the cowl and the beam, the rail-slide guiding system of the beam and the cowl exhibits a significant cantilever relative to the beam.
This configuration is not sustainable.
Indeed, during the deployment of the movable cowl during the thrust reversal phase, there are risks of jamming of the rail in the slide.
Thereby, the cantilever, of about 500 mm, requires multiplying the width of the considered rail, in order to avoid any risk of jamming of the rail in the slide.
However, this enlargement of the rail results in the lengthening of the corresponding slide on the beam, and consequently a modification of the external aerodynamic lines of the nacelle.
This impact on the aerodynamic lines is an unacceptable consequence insofar as this results in an increase of drag and hence a decrease of the aerodynamic performances of the thrust reverser in direct jet and an approaching of the thrust reverser toward the wing of the aircraft.
Then, it becomes impossible for the constructor to hold the clearances with the wing, which are required by the aircraft manufacturer.
In addition, such a slidably guiding structure of the half-cowls in a long cantilever offers much flexibility to the nacelle, thereby making it more sensitive to deformations.
Thereby, it is necessary to control the resistance to loads of the assembly, in particular to fatigue, by imposing productions in composite materials.
However, such composite materials imply complex and costly design developments.